DE69317859T2 - Air conditioning and cooling systems using a cryogen - Google Patents

Description

TECHNICAL FIELD

The invention relates generally to air conditioning and refrigeration systems and more particularly to the use of a cryogen to control the temperature of a conditioned space associated with stationary and transport applications of air conditioning and refrigeration systems.

BACKGROUND TECHNOLOGY

Stationary and transportation applications of air conditioning and refrigeration systems control the temperature of a conditioned space to a predetermined temperature range adjacent to a selected set point temperature, with transportation applications including such systems associated with a vehicle such as a straight truck, tractor-trailer combination, refrigerated container, and the like. Such systems typically use a chlorofluorocarbon (CFC) refrigerant in a mechanical refrigeration cycle. The mechanical refrigeration cycle requires a refrigerant compressor driven by a power machine, often including a dedicated internal combustion engine such as a diesel engine. Because of the suspected depleting effect of CFCs on stratospheric ozone (03), practical alternatives to the use of CFCs are being sought.

Prior art document US-A-3823568 describes a method for use in land and water vehicles using cryogenic fuels where the liquefied fuel is heated and vaporized in an air duct leading to the passenger compartment of the vehicle. This is accomplished by controlling the volume and temperature of the air supplied to the section of air duct containing the fuel. The vaporization of the fuel cools the air which is then introduced into the passenger compartment to cool the compartment.

The use of a cryogen, ie a gas that has been compressed into a very cold liquid state, such as carbon dioxide (CO₂) and nitrogen (N₂) is particularly attractive in air conditioning and refrigeration systems, as in addition to Eliminating the need for a CFC also eliminates the need for a compressor and associated prime mover. Air conditioning and refrigeration systems known to us that utilize a cryogen perform a cooling cycle by circulating the cryogen through a fluid path that includes a heat exchanger that is in heat exchange relationship with air from a conditioned space. When a warming cycle is required to maintain the temperature of the conditioned space within a predetermined narrow temperature band adjacent to a selected set point temperature, or a defrost cycle is required, then the cryogen is heated by a burner and associated fuel, and the heated cryogen is circulated through the fluid path and heat exchanger. Thus, cryogen is exhausted to the atmosphere during a cooling cycle, and cryogen plus a fuel, such as propane, diesel fuel, liquid natural gas, and the like, are exhausted to the atmosphere to perform warming and defrost cycles.

It would be desirable, and it is an object of the present invention, to provide new and improved cryogen-based air conditioning and refrigeration systems which utilize cryogen more efficiently and economically for operation at lower cost and also for extended operating time for a given vessel of cryogen.

SUMMARY OF THE INVENTION

Briefly, the present invention is an air conditioning and refrigeration system for controlling the temperature of a conditioned space utilizing a cryogen via heating, cooling and zero cycles as required to achieve and maintain the temperature within a predetermined narrow temperature band adjacent to a selected set point temperature. The refrigeration system includes a cryogenic refrigeration means, the cryogenic refrigeration means including a combustible fuel in a liquid, cryogenic state. The first heat exchange means is disposed in heat transfer relationship with the conditioned space, the second heat exchange means is disposed in heat transfer relationship with the cryogenic refrigeration means, and means is provided for interconnecting the first and second heat exchange means to utilize the cryogenic aspect of the fuel to effect the cooling cycle. A heating means is also provided, with a third heat exchange means arranged in heat transfer relationship with the heating means. Means interconnecting the first and third heat exchange means to effect the heating cycle. The heating means includes means for utilizing the combustible aspect of the fuel to provide heat during a heating cycle.

In further developments of the invention associated with an internal combustion engine, a means is provided for vaporizing the liquid cryogenic fuel, and additional means connects the vaporized fuel to the internal combustion engine for operation thereof from the cryogenic fuel supply.

In another development of the invention including an internal combustion engine, air moving means is provided for circulating air between the conditioned space and the first heat exchange means, the air moving means including a vapor engine. Means is provided for vaporizing the cryogenic fuel, the vapor engine being operated by expanding the vaporized fuel therein, and the internal combustion engine being operated via the expanded vaporized fuel.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will become more apparent from reading the following detailed description in conjunction with the drawings, shown by way of example only, in which: Figure 1 is a diagrammatic representation of a cooling system and internal combustion engine fuel storage arrangement constructed in accordance with a first embodiment of the invention, including a cryogenic coolant including a combustible fuel in a liquid cryogenic state used to effect cooling and heating cycles and also to operate the vehicle engine;

Figure 2 is a diagrammatic representation of a cooling system similar to that of Figure 1, except illustrating additional aspects and embodiments of the invention; and

Figure 3 is a diagrammatic representation of a cooling system constructed according to yet another embodiment of the invention in which an internal combustion engine powered by fuel derived from a cryogenic state thereof is dedicated to the cooling system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As used in the following description and claims, the term "conditioned space" includes any space that is to be controlled as to temperature and humidity, including stationary and transportation applications for the preservation of food and other perishables, maintenance of a proper atmosphere for the shipping of industrial products, room conditioning for human comfort, and the like. The term "refrigeration system" is used to generally include air conditioning systems for human comfort and refrigeration systems for preservation of perishables and shipping of industrial products. Furthermore, if it is stated that the temperature of a conditioned space is controlled to a selected set point temperature, then it should be understood that the temperature of the conditioned space is controlled to a predetermined range of temperatures besides the selected set point temperature. In the figures, valves that are normally open (n.o.) are shown with an empty circle and valves that are normally closed (n.c.) are shown with an "X" in a circle. The associated electrical or electronic control, hereinafter referred to as "electrical control", can of course be changed to reverse the off states shown. An arrow pointed to a valve in the figures indicates that the valve is controlled by or can be controlled by the electrical control.

The invention is suitable for use when the cooling system is associated with a single conditioned room which is controlled to a selected set point temperature is to be controlled; and the invention is also suitable for use when the refrigeration system 10 is associated with a compartmented conditioned space, ie, when at least first and second separate conditioned spaces are provided which are to be individually controlled to selected set point temperatures. In a compartmented application, for example, one conditioned space may be used to condition a frozen load and the other a fresh load, or combinations thereof as desired.

Referring now to the drawings, and particularly to Figure 1, there is shown a refrigeration system 10 suitable for use with any conditioned space, and particularly well suited for use on straight trucks, tractor-trailer combinations, containers, and the like, the word "vehicle" being used to refer generally to the various transportation vehicles utilizing refrigeration systems.

The cooling system 10 can be used in stationary and transportation applications, where the reference numeral 12 indicates a vehicle in a transportation application, and simply an insulated wall in a stationary application. The cooling system 10 can be associated with a single conditioned space 4 that is to be controlled to a preselected set point temperature, and the cooling system 10 can be associated with a compartmentalized application that includes two or more separate conditioned spaces 14 and 15 that are to be individually controlled to selected set point temperatures. The conditioned space 15 is also called an conditioned space and air conditioning device 15, since the reference 15 is used to refer generally to an conditioned space and an associated air conditioning device, including a heat exchanger to condition the space.

The cooling system 10 includes a cryogenic cooling means 13. The cryogenic cooling means 13 includes a vessel 16 containing a combustible fuel 17 in a cryogenic state, liquid and vapor phases of which are indicated at 18 and 20, respectively. In a preferred In accordance with one embodiment of the invention, the fuel 17 is liquid natural gas (LNG), which is primarily methane (CH4 ). However, any fuel available in a cryogenic state may be used, including propane (C3 H8 ) and ethane (C2 H6 ). The vessel 16 may be filled, for example, by connecting an earth support device, shown generally at 22, to a supply line or pipeline 24 which includes a valve 26.

The vapor pressure in the vessel 16 is maintained above a predetermined value by a pressure building and regulating arrangement 28 in which pipes 30 and 3 connect the pressurizing means 33 to lower and upper locations of the vessel 16, respectively. Pipe 30 connecting a lower location of the vessel 16 to the pressurizing means 33 includes a valve 32. The pressurizing means 33 includes an evaporating coil 34 which may be directly exposed to ambient temperatures or which may be located in a housing 35 for purposes explained below. Pipe 31 connecting the pressurizing means 33 to a high location of the vessel 16 includes a pressure regulating valve 36. The valve 36 maintains the steam pressure in the vessel 16 at a predetermined level which can be determined and selected if necessary each time the vessel 16 is filled. A pressure sensing safety valve 38 is provided in the pipe 31 at a sensing cell where the steam pressure in the vessel can be directly sensed. A vent valve 40 is also provided to facilitate the filling process. The valve 40 can be connected to the earth support device 22 during filling if desired.

The valve 32 opens when the pressure in the vessel 16 falls to a predetermined value to allow the cryogen to flow into the pressurization assembly 28. The predetermined value selected is based on factors such as the optimal delivery system pressure and performance.

As previously stated, the valve 32 admits liquid cryogen into the vaporizing coil 34, and the vaporizing coil 34 is exposed to the ambient temperature outside the vehicle 12. As in the co-pending As described in United States application Serial No. 07/982,333, heat produced during normal operation of a refrigeration system can be used to enhance the vapor producing capabilities of ambient loops such as the evaporative coil 34. Thus, the evaporative coil 34 can be subjected to temperatures higher than ambient, particularly during low ambient temperature conditions, by using gases produced as a product of the combustion of vaporized fuel 20 during the warm-up and defrost circuits; or by using a heated liquid coolant associated with an internal combustion engine 41.

In the embodiment of the invention set forth in Figure 1, the internal combustion engine 41 is associated with the vehicle 12, such as by being connected to a vehicle drive train 43 that drives the vehicle 16, and so the cooling system 10 is shown in a transportation application. If the cooling system 10 is associated with a refrigerated container, then the engine 41, rather than being a vehicle drive motor, may be the prime mover for an electrical "generator set" package that is used until the container is transported to a location having a source of electrical potential.

Using LNG as an example of a suitable fuel 17 in cryogenic form, the vessel 16 can be filled with LNG at an initial pressure of about 21 bar (300 psia) and an initial temperature of about -160ºF (-107ºC), which will satisfy the low temperature end of the usual temperature control range of most refrigeration systems, including transportation applications. Of course, other pressures and temperatures than those set forth in this example may be used, provided that the temperature of the cryogen is low enough to maintain the desired set point temperature or temperatures in the associated conditioned space or spaces.

The present invention includes a fluid flow path 42, called a "closed" fluid flow path because it is completely isolated from any direct contact with the cryogenic fuel 17 and from any direct contact with the air in the conditioned space 14. The closed fluid flow path 42 may be at atmospheric pressure or pressurized as desired. The closed fluid flow path 42 includes a first portion 44 having a first heat exchanger 46. The first part 44 extends between tees 48 and 50, the first part 44 including from tee 48 to tee 50 a conduit 52, an optional location for a pump, designated 54', as a preferred location is designated 54, a conduit 56, a fitting 58, a flow control valve 60, a conduit 62, the first heat exchanger 46, a conduit 64, a fitting 66, a valve 67, a fitting 68, a conduit 70, the preferred location for the pump 54, and a conduit 75.

The closed fluid flow path 42 includes second and third portions 74 and 76 closed in parallel with the first portion 44, each extending between tees 48 and 50. The second portion 74 includes a second heat exchanger 78. The second heat exchanger 78 is connected between tees 50 and 48 via a conduit 80 including a valve 82 and a conduit 84 including a valve 86. The second heat exchanger 78 is shown disposed within the vessel 16 in direct heat exchange relationship with the cryogen 8, but the second heat exchanger 78 may be disposed in heat exchange relationship with a wall 87 of the vessel 16, as shown in Figures 2 and 3. The third portion 76 includes a third heat exchanger 88. The third heat exchanger 88 is connected via a pipe 90 and a pipe 92, which includes a valve 94, between the T-pieces 50 and 48.

The second conditioned space and the air conditioning device 15 is connected in a compartmentalized application in a first embodiment thereof via pipes 96 and 98 between the connectors 66 and 68, wherein one of the conduits, such as conduit 98, includes a flow control valve 100. Valve 67 is closed when apparatus 15 is in operation.

In a second embodiment, the device is connected to the first heat exchanger 46 in parallel, rather than in series. In this other embodiment, the connection to the pipe 96 is made by the fitting 58 in the pipe 56, rather than by the fitting 66 in the pipe 64. The valve 67 can be replaced by a check valve in the second embodiment.

An expansion and filling tank 102 is connected to the fitting 68 to fill the closed fluid flow path 42 with a heat exchange or secondary fluid 104 and also to allow temperature induced expansion and contraction of the secondary fluid 104. The tank 102 and the closed fluid flow path may be pressurized depending on the specific secondary fluid selected. The secondary fluid 104 should be a wide range liquid coolant selected to have good heat transfer and transport properties while remaining in a liquid state during the various temperatures to which it is exposed. Examples of suitable fluid for the secondary fluid include ethylene glycol and D-limonene, the latter being a trade name of Florida Chemical Co., Inc., Lake Alfred, Florida.

The first heat exchanger 46 is associated with an air conditioning means or device 108 which includes an air moving means 110. The air moving means 110 includes a fan or blower 12 driven by a suitable motor 114. In a preferred embodiment of the invention, the motor 114 is a steam driven motor driven by vaporized cryogen 20 obtained from the storage vessel 16 by arrangements explained below. The air conditioning means 108 directs conditioned air or discharge air, indicated by arrow 116, into the conditioned space 14 via an opening 118 in a wall 120 of the vehicle 12.

Return air from the conditioned space 14, indicated by arrow 122, is drawn by the air moving means 110 through the opening 118 and into heat exchange relationship with the first heat exchanger 46. The resulting conditioned air 116 is discharged back into the conditioned space via the opening 118 and a discharge chamber that separates return air from the discharge air.

The electrical controller 124 is provided for controlling the temperature of the conditioned space 14 to a predetermined set point temperature selected by a set point selector 126. The electrical controller 124 controls the temperature of the conditioned space 14 via cooling and heating circuits, and the electrical controller 124 also initiates a defrost circuit to remove water ice buildup on the heat exchanger 46 and a heat exchanger associated with the device via a heating circuit. If it is desired that the air moving means 110 remain in operation during a defrost cycle, then a controllable damper 128 is provided which closes the opening 118 during defrost.

The electrical controller 124 receives inputs from a return air sensor 130, a discharge air temperature sensor 132, a coil temperature sensor 134, an ambient air temperature sensor 136, and a pressure sensor associated with the vessel 16, such as via control line 135 from the pressure reading valve 38. If more than one conditioned space is being conditioned, such as the additional conditioned space and air conditioning device generally indicated at 15, then a set point temperature selector is also provided for each additional conditioned space, such as a set point temperature selector 138 for the conditioned space 15. The additional conditioned space and associated air conditioning device 15 may be constructed in the same manner as the conditioned space 14 and associated air conditioning means 108, and is not shown in detail. Fan or fans in the additional air-conditioned rooms may be driven by electric, hydraulic, pneumatic, or steam motors as desired.

The return air temperature, the discharge air temperature, and the ambient air temperature determine when the electrical controller 124 commands cooling and heating cycles, and the temperature of the coil surface of the first heat exchanger 46, sensed by the sensor 134, can be used to determine when a defrost cycle should be initiated. A defrost cycle can also be initiated by other means, such as by a timer, by a manually operated switch, by a programmed algorithm, and the like.

The second heat exchanger 78 is associated with the cryogenic coolant 13, removes heat from the secondary fluid 104, and transfers the heat to the liquid cryogen 18. The second heat exchanger 78 may be constructed as shown in Figure 1, with a plurality of coil windings or loops disposed in and near the bottom of a metallic tank wall 87 of the vessel 16. Thus, the coils or loops 140 of the heat exchanger are immersed in the liquid cryogen 18 within the vessel 16. Thermal insulation 144 surrounds the inner tank 142, or a vacuum tank may be used. A suitable alternative assembly for the second heat exchanger 78 is shown in Figures 2 and 3, which alternative arrangement has a plurality of windings or loops 140' in thermal contact with the outside surface of the tank wall 87 of the vessel 16, surrounded by the thermal insulation 144.

The third heat exchanger 88 includes a plurality of coil windings or loops 146 disposed in a suitable housing 147. The coil windings 146 are heated by a heating means 148. The heating means 148 includes a burner 150. Vaporized fuel 20 from the vessel 16 is selectively directed to the burner 150 via a conduit 152 and a valve 154, as explained below. When the electrical controller 124 opens the valve 154 to permit heating of the coil windings 146 and the secondary fluid 104 therein, then the burner 150 is simultaneously ignited to provide a flame indicated at 56. In stationary applications, other suitable heat sources may be used to heat the cryogen, including electrical, hot liquids, and hot waste gases.

Vaporized cryogen 20 for the burner 150 and also for operating the steam engine 114 and the combustion engine 41 in the embodiment of Figure 1, can be supplied by tapping the piping 31, regardless of whether the electrical controller 124 commands cooling or heating circuits in the conditioned spaces 14 and 15. The piping 31 can be tapped, for example, via a T-piece 158, which draws vaporized cryogen 20 from the vessel 16 and from the pressurization and control assembly 28.

An input side of the steam engine 114 is connected to the tee 158 via a pipe 168, and an output side of the steam engine 114 is connected to the previously mentioned pipe 152. If the demand for vaporized cryogen 20 increases, then additional vaporized cryogen can be supplied by an arrangement that includes tapping the liquid pipe 30 with a tee 174, tapping the pipe 168 with a tee 176, and connecting an ambient coil or loop 178 via a valve 180 between the tees 74 and 176. When the valve 180 is opened by the controller 124, then the ambient loop 178 vaporizes liquid cryogen 18, adding to the available supply of vaporized cryogen.

As previously discussed, additional vaporized cryogen can be supplied without requiring the addition of the ambient loop 178 by utilizing heat generated by the cooling system 10 during normal operation thereof to enhance heating of the vaporizing coil 34. This arrangement is particularly advantageous during low ambient temperatures. Withdrawing vaporized cryogen 20 from the vessel 16 is also more desirable than withdrawing liquid cryogen 18 from the vessel 16 via the ambient loop 178 because the heat of the vaporizing heat from the liquid Cryogen 18 is removed. For example, as shown in Figure 1, hot gases produced by the burner 150 may be directed from the heater housing 147 via a conduit 179 and a valve 181 to the vaporizing housing 35. On the other hand, as described below relative to Figures 2 and 3, heated liquid coolant associated with the internal combustion engine 41 may be directed into heat exchange relationship with the vaporizing coil 34. When supplied, the ambient coil may be heated with byproduct heat in the same manner as just described relative to the vaporizing coil 34.

The pump 54 may be driven by the steam engine 114, as shown in Figure 1 by a pulley and belt arrangement 182, or by an associated internal combustion engine, as described below relative to Figure 3. The pump 54 may also be driven by a motor such as an electric, hydraulic or pneumatic motor. If an electric motor is used, then a suitable source of electrical power for the motor is described below relative to Figure 3.

As shown in Figure 1, the internal combustion engine 41 is preferably operated using vaporized fuel 20 from the cryogenic medium 13. The engine 41 may, for example, use vaporized fuel after it has been expanded in the steam engine 114. If the steam leaving the steam engine 114 is cold enough, it may be passed through a separate path through the heat exchanger 46, or the heat exchanger associated with the apparatus 15, to gain an additional cooling benefit before the steam is directed to the internal combustion engine 41. The conduit 152 may be tapped with a tee 184, and the tee 184 may be connected to the engine 41 via a conduit 186 including a pressure regulating valve 188. Sufficient vaporized fuel 20 is ensured by tapping the pipes 168 and 186 with T-pieces 190 and 192 respectively, and connecting a pipe 193 therebetween which includes a valve 194 and an expansion valve 195 which may have a fixed or controlled orifice to provide approximately the same pressure drop as provided by the steam engine 114.

Tees may be provided in the fluid flow path portion 44 as described in co-pending United States applications Serial Nos. 07/982370 and 07/982548. When the cooling system 10 is associated with an application requiring air conditioning and refrigeration, such as a transportation application in which the vehicle 12 includes, in addition to the conditioned space 14, the cab is to be air conditioned via the secondary fluid 104 while the vehicle 12 is parked and occupied, eliminating the need to operate the vehicle engine 41. The tees in the fluid flow portion 44 allow secondary fluid 104 to be selectively circulated through a heat exchanger associated with such a cab.

When the electrical controller 124 detects the need for a cooling circuit in the conditioned space 14 to maintain the temperature selected on the set point temperature selector 126, the electrical controller 124 energizes, thereby opening, valves 82 and 84, and the electrical controller 124 controls the flow control valve 60 to control the flow rate of the secondary fluid 104 through the first heat exchanger 46. Cooled secondary fluid 104 is pumped from the second heat exchanger 78 to the first heat exchanger 46 via conduits 84, 52, 56, and 62. Heat in the return air 122 from the conditioned space 14 is transferred to the secondary fluid 104, and the heated secondary fluid is pumped via conduits 64, 70, 75, and 80 to the second heat exchanger 78 where the heat is transferred to liquid cryogen 18, and then removed from the heat of vaporization thereof as liquid cryogen 18 vaporizes, providing vaporized cryogen 20 for operation of the steam engine 114, the burner 150, and the combustion engine 41.

If a second conditioned space and an air conditioning arrangement 15 is supplied in series with the heat exchanger 46, and a cooling circuit in the Device 15 is required, then flow control valve 100 is opened to allow secondary fluid in conduit 64 to flow through the associated heat exchanger. The temperature of a second conditioned space associated with air conditioning device 15 is selected via set point selector 138 to be a higher temperature conditioned space than conditioned space 14. For example, conditioned space 14 may contain a frozen load and the conditioned space indicated generally at 15 may contain a fresh load. If both conditioned spaces contain fresh loads, then conditioned space 14 would be associated with the lower temperature load.

When the device 15 is connected in parallel with the heat exchanger 46 via the fitting 58 and the piping 96', the valve 100 is opened by the electrical controller 124 to allow secondary fluid in the piping 56 to circulate through the associated heat exchanger. In this embodiment of the device 5, the device is not subject to the limitation of controlling to a higher temperature than that of the conditioned space 14.

If the air flow in the conditioned space 14 is insufficient during the cooling cycle, as detected by an air flow rate feedback sensor 203, or by a rate sensing means 207 associated with the steam engine 110, such as a gear and sensor arrangement, then the electrical controller 124 opens the valve 180 when the ambient loop 178 is supplied; or the controller 124 opens the valve 181; or the controller 124 opens a valve shown in Figure 3, which allows heated engine coolant to flow into heat exchange relation with the evaporating coil 34 when byproduct heat is arranged to improve the ability of the pressure regulating coil 34 to produce vaporized cryogen.

If a heating circuit is required to maintain the set point temperature in the conditioned space 14, then the electrical control 124 closes the Valves 82 and 86 to completely isolate the second heat exchanger 78 from the secondary fluid flow path 44, valves 94 and 154 are opened, and the burner 150 is ignited. The secondary fluid 104 is then pumped through the coil windings 146 of the third heat exchanger 88, with the heated secondary fluid 104 being directed to the first heat exchanger 46 via the now open valve 94 and conduits 52, 56, and 62. The secondary fluid 104 from the heat exchanger 46 is again directed back to the third heat exchanger 88 via conduits 64, 70, 75, and 90. A defrost circuit to defrost and remove water ice that may build up on the first heat exchanger 46 during a cooling cycle is similar to the heating circuit except that the damper 128, when supplied, is closed to prevent warm air from being released into the conditioned space 14; or, alternatively, the valve 170 may be closed during a defrost cycle to prevent the steam engine 114 from operating during a defrost cycle. The valve 194, if not already open, would be opened when the valve 170 is closed to ensure a flow of fuel to the burner 150 and the engine 41.

If the second conditioned space 15 requires heat during a heating cycle in the first conditioned space 14, then the valve 100 is controlled accordingly. If the conditioned space 14 is associated with a frozen load, then a heating cycle for the space 14 is not required, and a controllable bypass assembly 204 may be provided to allow the first heat exchanger 46 to be bypassed in the first or series arrangement of the apparatus 15. The bypass assembly 204 includes a fitting 58 in the conduit 56, and a conduit 208 disposed between the fitting 58 and the fitting 66, the conduit 208 including a valve 210. The bypass arrangement 204 also allows the electrical controller 124 to select a zero circuit in addition to the heating and cooling circuits when the conditioned space does not require a heating circuit or a cooling circuit to maintain the set point temperature. When the heat exchanger 46 requires defrost, and If device 5 requires a cooling circuit in the series embodiment of device 15, then heated fluid is passed through heat exchanger 46, bypassing device 15 by closing valve 100 and opening valve 67. If device 15 requires a defrost circuit while heat exchanger 46 requires a cooling circuit, then valves 60 and 67 are closed and valves 210 and 100 are opened. In the parallel embodiment of device 15, each parallel path is individually controlled as required to obtain the desired heating, cooling, or defrost circuits in the associated spaces. Thus, electrical controller 124 can serve the cooling, warming, and defrost requirements of conditioned spaces 14 and 15 by controlling valves 60, 67, 100, and 210 independently.

Figure 2 is a diagrammatic representation of a cooling system 212 that is similar to the cooling system 10 shown in Figure 1, except that it depicts a thermosyphon arrangement for circulating the secondary fluid 104, eliminating the need for the pump 54 of the embodiment of Figure 1. Like reference numbers in Figures 1 and 2 indicate like components and will not be described again relative to Figure 2. In the thermosyphon arrangement of Figure 2, it is important that the second heat exchanger 78' is located at a height higher than the height of the first heat exchanger 46 and that the first heat exchanger 46 is located at a height higher than the height of the third heat exchanger 88. The relative heights of the first, second and third heat exchangers 46, 78 and 88 are indicated at 214, 21 and 218 respectively.

In the thermosyphon arrangement of Figure 2, the secondary fluid leaving the first heat exchanger 46 will be warmer than the secondary fluid in the second heat exchanger 78 during a cooling cycle, providing thermal gradients that move the warmer secondary fluid up to the second heat exchanger 78 and the cooler secondary fluid from the second heat exchanger 78 down to the first heat exchanger 46. The valve 94 will be closed to prevent circulation through the heat exchanger 88. Similarly, the Valves 82 and 86 will be closed during a heating cycle and valve 94 will be open. The secondary fluid leaving the third heat exchanger 88 will be warmer than the secondary fluid in the first heat exchanger 46, providing thermal gradients that move the warmer secondary fluid up to the first heat exchanger 46 and the cooler secondary fluid in the first heat exchanger 46 down to the third heat exchanger 88.

Figure 2 also illustrates that a cooling water jacket 220 associated with the internal combustion engine 41 may be provided and connected to a heat exchanger 222 disposed in heat exchange relationship with the evaporating coil 34 of the pressurization and evaporation assembly 28. Coolant tubing 224 and 226 circulate heated engine coolant from the water jacket 220 through the heat exchanger 222 via a flow control valve 228. Instead of using the heat exchanger 222, a flooded configuration may be used in which the housing 35 contains the heated engine coolant in direct contact with the coil 34.

Figure 3 is a diagrammatic representation of a cooling system 230 constructed in accordance with another embodiment of the invention. Like reference numbers in Figures 1 and 3 indicate like components and so they will not be described again during the description of the embodiment in full Figure 3. The embodiment of Figure 3 illustrates that a cooling system may have a small internal combustion engine 232 dedicated to provide mechanical and electrical power for operating fans, ventilators, controls, and the like, with the dedicated internal combustion engine 232 powered by the cryogenic fuel 20. The tubing 168 is connected to a fitting 234, for example, via a pressure regulating valve 236, rather than being connected to the steam engine 114. The fitting 234 is connected to a first branch including a conduit 238 with a flow control valve 240, the first branch providing a supply of fuel for the dedicated engine 232.

The dedicated motor 232 drives an electrical generator or AC generator 242, such as a pulley-belt arrangement 244, and the electrical output of the generator 242 is connected to an electrical circuit 246 that maintains a battery in a fully charged state. The electrical circuit 246 also provides electrical power for other purposes, such as driving an electrical motor 250 connected to a fan 112 of the air mover 110'. The motor 232 may drive the pump 54, such as via a pulley-belt arrangement 252, or the pump 54 may be driven by an electrical motor connected to the circuit 246, as desired.

The connector 234 is connected to a second branch that includes the previously described heating means 148 via conductor 152. The connector 234 may be connected to a third branch 254 that is available for another device requiring vaporized fuel, such as a vehicle propulsion engine as described in the embodiments of Figures 1 and 2 or an engine associated with the generator set of a cooled vessel.

In a preferred embodiment of the invention, the associated internal combustion engine is started in response to the electrical controller 124, as indicated by the control output conductor 256, at a pressure just below the trigger setting of the valve 38 to vent cryogenic fuel from the vessel 16 in response to the vessel 16 reaching a predetermined pressure sensed by the valve 38. As previously stated, the electrical controller 124 senses the pressure level in the vessel 16 via the control input conductor 135. Starting the associated engine in response to pressure will reduce the pressure in the vessel 16, and preclude the venting of unburned fuel.

If the engine is the dedicated combustion engine 232 of Figure 3, then the engine 232 is always under the supervision of the electrical control 124, and the Engine 232 can be started and stopped whenever the controller deems necessary. If engine 41 is involved in driving a vehicle, then electrical controller 124 checks to determine if it is safe to start engine 41 before starting it for pressure control. Suitable sensors (not shown) provide inputs to electrical controller 124, with electrical controller making the decision as to whether it is safe to start engine 41 based on the sensor readings. Suitable sensors and logic circuitry for making the decision as to whether it is safe to remotely start an engine driving a vehicle are described in U.S. Patent 5,072,703.

Although not shown in Figures 2 and 3, the embodiments of the invention shown in Figures 2 and 3 can also use the multiple conditioned room arrangement of Figure 1. Furthermore, the embodiment of the invention shown in Figure 3 can use the thermosyphon arrangement of Figure 2 by arranging the second heat exchanger 78' at a higher elevation than the first heat exchanger 46, and by arranging the first heat exchanger 46 at a higher elevation than the third heat exchanger 88.

Although not shown in the figures, a pressure relief valve should be added at any point where cryogen may be trapped between two valves during shutdown to prevent excessive pressures from building up.

Claims (22)

1. Cooling system (10) associated with a conditioned space (14) to be controlled to a predetermined set point temperature (126) via heating and cooling circuits, the system comprising: a cryogenic cooling agent (13), wherein the cryogenic cooling means includes a fuel (18) in a cryogenic state, a first heat exchange means (46) in a heat exchange relationship with the air-conditioned space, a second heat exchange means (76) in a heat exchange relationship with the cryogenic cooling means, means (74,44) interconnecting the first and second heat exchange means to provide a cooling circuit, a heating agent (148), a third heat exchange means (88) in a heat exchange relationship with the heating means, and means (76,44) interconnecting the first and third heat exchange means to provide a heating circuit, wherein the heating means (148) includes means (150) for utilizing fuel from the cryogenic cooling means during a heating cycle. 2 A cooling system according to claim 1, in which the cryogenic fuel includes a liquid phase (18) and which includes: a combustion engine (41), a means (28) for vaporising the liquid fuel, and means (68, 19,186) for connecting the vaporized liquid fuel to the internal combustion engine. 3. Cooling system according to claim 2, in which the cooling system is a transport cooling system associated with a vehicle, the internal combustion engine being associated with the vehicle. 4. A cooling system according to claim 1, wherein the cryogenic fuel includes a liquid phase (18) and which includes: an internal combustion engine (41), an air movement means (110) for circulating air (122) between the conditioned space (14) and the first heat exchange means (46), wherein the air moving means includes a steam engine (114), a means (28) for vaporizing the liquid fuel, means (168, 170) for directing vaporized fuel to the steam engine to operate the steam engine by expanding the vaporized fuel therein, and means (184, 86) for directing vaporized fuel from the steam engine to the internal combustion engine to operate the internal combustion engine with the expanded vaporized fuel. 5. Cooling system according to claim 4, in which the cooling system is a transport cooling system associated with a vehicle, the internal combustion engine being associated with the vehicle. 6. A cooling system according to claim 1, wherein the means connecting the first and second heat exchangers includes: a fluid flow path (42) having a pre-summed secondary fluid (104) therein, means (54,214,216,218) for circulating the secondary fluid in the fluid flow path, and control means (124) for arranging the fluid flow path so that the secondary fluid circulates between the first and second heat exchange means during a cooling cycle. 7. Cooling system according to claim 6, in which the control means (124) arranges the fluid flow path (42) so that the secondary fluid (104) during a heating circuit between the first and third heat exchange means. 8. A cooling system according to claim 6, wherein the means for circulating the fluid (104) in the fluid flow path (42) includes a pump (54; 54'). 9. A cooling system according to claim 8, wherein the cryogenic fuel includes a liquid state (18) and which includes: an air movement means (110) for circulating air (122,116) between the conditioned space (14) and the first heat exchange means (46), wherein the air moving means includes a steam engine (114), a means (28) for vaporizing the liquid fuel, means (168) for directing the vaporized fuel to the steam engine to operate the steam engine by expanding the vaporized fuel therein, and means (182) for operatively connecting the steam engine and the pump (54'). 10. A cooling system according to claim 6, wherein the means for circulating the fluid in the fluid flow path includes a thermosyphon arrangement (214,216,218) in which the first heat exchange means (46) is arranged at a lower level than the second heat exchange means (78). 11. A cooling system according to claim 7, wherein the means for circulating the fluid in the fluid flow path includes a thermosyphon arrangement (214,216,218) in which the first heat exchange means (46) is arranged at a lower level than the second heat exchange means (78) and at a higher level than the third heat exchange means (88). 12. A cooling system according to claim 1, wherein the cryogenic fuel includes a liquid phase (18), and which includes the following. an internal combustion engine (232), a means (28) for vaporising the liquid fuel, a means (168) for directing the vaporized fuel to the internal combustion engine, in order to operate the internal combustion engine therewith, an electric generator means (242) driven by the internal combustion engine, and an air movement means (110') for circulating air between the air-conditioned space and the first heat exchange means, wherein the air moving means includes an electric motor (250) powered by the electric generator means. 13. A cooling system according to claim 12, wherein the means connecting the first and second heat exchangers together includes: a fluid flow path (42) having a predetermined secondary fluid (104) therein, a pumping means (54) for circulating the secondary fluid into the fluid flow path, and a control means (124) for arranging the fluid flow path so that the secondary fluid circulates between the first and second heat exchange means during a cooling cycle, wherein the pumping means (54) is driven (252) by the internal combustion engine. 14. A refrigeration system according to claim 1, wherein the cryogenic fuel includes a liquid phase (18), and including the following. an internal combustion engine (232), a means (28) for vaporising the liquid fuel, a means (168) for directing the vaporized fuel to the internal combustion engine, in order to operate the internal combustion engine therewith, an electric generator means (242) driven by the internal combustion engine, and an air movement means (110') for circulating air between the conditioned space (14) and the first heat exchange means (46), wherein the air moving means includes an electric motor (250) driven by the electric generator means, and wherein the heating means (148) includes burner means (150) for utilizing a portion of the vaporized fuel to provide heat during a heating cycle. 15. A cooling system according to claim 14, wherein the means interconnecting the first and second heat exchanger means includes; a fluid flow path (42) having a predetermined secondary fluid (104) therein, pumping means (54) for circulating the secondary fluid in the fluid flow path, and control means (124) for arranging the fluid flow so that the secondary fluid circulates between the first and second heat exchange means during a cooling cycle, wherein the pumping means is driven by the internal combustion engine (252). 16. A cooling system according to claim 15, wherein the predetermined fluid (104) is a liquid having a characteristic of remaining in a liquid state while being circulated in the fluid flow path. 17. A cooling system according to claim 15, wherein the cryogenic cooling means includes a storage vessel (16) containing the fuel in a cryogenic state including a liquid phase (18), the second heat exchange means being in heat exchange relationship with the storage vessel. 18. The refrigeration system of claim 1 including an air moving means (110) that circulates air between the conditioned space (14) and the first heat exchange means (46), the air moving means including a steam engine (114). and wherein the cryogenic cooling means includes a storage vessel (16) containing the liquid fuel (18) in the cryogenic state and including a pressurization means (28) that vaporizes liquid cryogen from the storage vessel, the vaporized cryogen maintaining a predetermined minimum pressure in the storage vessel and also providing vaporized cryogen that is expanded in the steam engine. 19. A cooling system according to claim 18 including an internal combustion engine (41), wherein the internal combustion engine is powered by the expanded vaporized cryogen. 20. A cooling system according to claim 19, wherein the internal combustion engine includes a liquid coolant (220) that is heated during operation of the internal combustion engine and includes means (224,226,228) directing the heated liquid coolant in a heat exchange relationship with the pressurizing means (28) to enhance the conversion of liquid cryogen to vaporized cryogen. 21. A refrigeration system according to claim 1 including air moving means (110) circulating air (116,222) between the conditioned space (14) and the first heat exchange means (46), the air moving means including a steam engine (114), and wherein the cryogenic cooling means (13) includes a storage vessel (16) containing the liquid fuel (18) in the cryogenic state including a liquid phase and including means (28) for vaporizing the liquid cryogen and means (168) for directing the vaporized cryogen to the steam engine means. 22. A cooling system according to claim 1, in which the cryogenic fuel includes a liquid phase (18) in a storage vessel (16), and which includes: an internal combustion engine (41232), means (28) for vaporizing the liquid fuel, a means (168,193,186,168,238) for connecting the vaporized liquid fuel to the combustion engine, a means (38,135) for detecting the pressure in the storage vessel, and means (124) for starting the internal combustion engine in response to predetermined conditions including the pressure in the reservoir.